Found the solution at: http://community.wd.com/t5/WD-My-Cloud-EX4/RAID-rebuild-taking-days-weeks-months-not-working/td-p/737144
Enter with PuTTY.
Type:
$ cat /proc/mdstat
See the 1031K/sec cap and swear.
Run:
$ sysctl -w dev.raid.speed_limit_min=100000
Then run again:
$ cat /proc/mdstat
and see that it’s much quicker now. Your rebuild will be done in a few hours.
This is not the first, not the second huge f*ck-up from WD regarding their MyCloud EX2. Avoid the product if you still can.
